Hi all, the car has again failed emissions, on a HC reading of 89 against a maximum permitted 80. It's on it's third 'cat' in 6 years ! It was throwing ,a heated O2 sensor code but the mechanic says that it would not affect the hydro-carbons, is he right ? What else could it be ?........Roger.

 

A failed O2 sensor could cause excess fuel to be dumped into the engine. DOn't know if that would necessarily give a high HC count, but I would almost suspect it would. Does it seem to be burning rich?

 

An sensor fault will more than likely affect emissions as the ECM will then default to the default fueling tables to protect the engine. Fix the sensor first and then recheck before considering throwing more parts at it.

 

A bad O2 sensor could cause the hydrocarbon emissions to increase. It's not the first thing that I would think to check, but, if it's setting a fault code it's worth diagnosing. There's a diagnostic proceduire that is mandated for licensed test and repair technicians in California. One of the steps is to check for fault codes and repair as needed.

Before this step, I would make sure that you don't have any ignition or mechanical issues like uneven compression, bad/fouled plugs, vacuum leaks and so forth. H/C's are unburned fuel so anything that will cause a misfire will raise this reading. If you have a rich mixture, it can cause H/C and C/O readings to increase. A lean mixture can cause a lean misfire and a higher H/C reading.

Can you post all of the gas readings on the Vehicle Inspection Report? Sometimes the other readings can put your H/C readings into context. Another great tool is a lambda calculator. This link is a great way to determine if your mixture is rich or lean.

http://www.smogsite.com/calculators.html

Scroll down the page to find the Lambda Calculator. Plug in your readings and calculate your lambda numbers. We can help you interpret the results once you post your readings.

 

I don't know what you had been done trouble shooting on your car but anyways, I would recomment these things need to do first before doing further trouble shooting, otherwise your head will spin like nuts with your money.
1/ Tune up: spark plugs, Wire set, distrubutor cap, distrubutive rotor, check map air flow sensor...
2/ Inspect all vacuum line for cracking, loosing...
3/ If step 1 & 2 has been done, you need to replace bot oxyzen sensor band 1&2.
4/ If all step above has been done but still fail high H/C, I would suspect the ignition system. Weak ignition coil can cause misfire, engine run hot, unburnt gas remain too much in CAT. Once too much unburnt gas in the CAT, you will have high % of H/C and CO.

 

To gdstock, plums, jcchavez76 and zenidyle.Thank you all, very much. OK, cchavez76, funnily enough, it was the smog station on Sepulveda and Culver Blvd in Culver City that did the test. The Lambda readings come out to 0.987, with air/fuel ratio of 14.51. Any suggestions will be appreciated.........Roger.

 

Hey neighbor,

"It's a small world after all."

The lambda reading indicates that your mixture is not excessively rich or lean at the moment the exhaust gas readings were recorded. It's still possible that your O2 sensor could be contributing to your high H/C. It could be switching too slow and causing the mixture to be corrected too slowly.

Can you post all of the readings on the Vehicle Inspection Report? Together, they can better indicate a possible cause of the failing readings. For example; if the O2 readings are above 1% and CO2 readings are 13.5% under load and you have only a slightly high H/C reading, this could indicate a failing catalyst. If the CO2 is higher around 15% and O2 is almost 0%, your catalyst is probably not the cause.

Post all of the gas readings and we'll take it from there. I think your car should have been tested on the dynamometer at 15 and 25 mph. If so, please post both exhaust sample readings.

 

Next time you bring it to be tested make sure that the motor is hot,cold motors tend to run richer,thus bad readings.

 

Your lamda is readings come out to 0.987(v) constant that mean it's running RICH. In order to measure accurated, you have to let the engine run little while, engine temperature rise up the normal, the lamda sensor perform the "open loop" atleast 250 °C to 500 °C.
Sensor output ranges from 0.2 volts (lean) to 0.8 volts (rich). A perfectly balanced or "stoichiometric" fuel mixture of 14.7 parts of air to 1 part of fuel gives an average reading of around 0.45 volts.
The lambda sensor’s output voltage doesn't remain constant, however. It flip-flops back and forth from rich to lean. Every time the voltage reverses itself and goes from high to low or vice versa, it’s called a “cross count”. A good O2 sensor on a injection system should fluctuate from rich to lean about 1 per second. If the number of cross counts is lower than this, it tells you the O2 sensor is getting sluggish and needs to be replaced.
If the sensor’s output voltage never gets higher than 0.60 V and never drops to less than 0.30 V, it needs to be replaced. The same is true if the sensor’s output is sluggish or doesn't change.
So, you don't need to replace both sensor on both up stream or down stream. You have to make sure which sensor is bad and place itself. But if both indicate weak, fail, so you have to replace them all. Good lucks.

 

Thanks so much guys. I've ordered a new heated O2 sensor (a third the price, on line, compared to Autozone). Test results were as follows:


Nov 9th '12................... Nov 30th '10



15 mph__ 25 mph............ 15mph__ 25mph

CO2 14.7__ 14.8............... CO2 14.8__ 14.8

O2 0.0__ 0.0.................... O2 0.0__ 0.0

HC 89__ 38...................... HC 80__ 41

CO 0.34__ 0.28.................CO 0.07__ 0.07

NO 134__ 2...................... NO 0__ 0


So, you see, a huge increase in NOX and CO. Before it just scrapped through on HC, being the maximum allowed. Plugs,points, cap,leads, all look good........Roger.PS..Sorry about the way the tables came out,I didn't type them close together, IT did it. Also the '10 readings were just after another new cat was installed.OK, found a way to keep tables apart.

 

In the first your post say: "....It's on it's third 'cat' in 6 years !....". My question is Why did you replace 3 CAT in 6 years? a CAT should be reliable life time ( assume: 100,000 mile). You should rather find out the culprit to kill your CAT than replacement it.
Second post say: ".......The Lambda readings come out to 0.987......" This data help me determine that your engine run rich. So there is excessive unburnt gas draw into CAT. This excessive unburnt gas will be reburnt at CAT that's why your CAT is easyly detroyed.
Third post you say: "....a huge increase in NOX and CO. Before it just scrapped through on HC, being the maximum allowed....." . This data help me determine that your engine run too hot because Nitrous Oxide or NO is produced only when an engine's combustion chamber temperature reaches over 2500F. And Carbon Monoxides or CO is produced only when HC is unburnt completely during chemical reaction change form that's meam carbon in HC is not completely burnt off and produce CO. ( HC + O2 -----> CO2 + H2O + CO)
Combine all data above, I think your emission system is malfunction. In order to find out the culprit, there is a lot of works for you.

I/ So, first of all, we are going to fix the engine produce too much NOx
(Before to do all trouble shooting below, I assume that you already tuned up like I mention previous post.)
1/ I would suggest that you need to check or replace Engine Coolant Temperator first because it's cheaper than other components.
2/ Check and replace thermostate.
3/ Flush and replace the engine coolant.
4/ Check all vacuum for cracking, loosing connection.
5/ Check and clean EGR valve. I don't want you through it away because it's too expensive unless you know for sure that its culprit.

II/ Second, we are going to fix the engine produce too much CO
(Before to do all trouble shooting below, I assume that you already tuned up like I mention previous post.)
it's good thing that you did replace O2. We rule out them.
1/ Check and replace MAP sensor.
2/ Check and replace TPS.
Good lucks.

 

I did did the lambda calculations on all of the readings you posted and they do all trend rich. Zenidyle is right about that. If you trend rich for a long time, it will degrade the catalyst sooner. The aftermarket cats will generally degrade faster than the factory cats.

The 02 readings you post tell me that your cat is probably doing a good job. Like Zenidyle said, your asking it to do too much. The O2 sensor could very well be the culprit. It still works but may be too slow and or biased lean and resulting in a rich correction.

I would test or replace the O2 sensor and then retest the emissions. When you get the new sensor, be careful to only use a small amount of anti seize on the threads only. Don't get the anti seize on other part of the sensor. Most sensors come with this stuff and they give you way more than you need. It can contaminate the sensor and cause it work like a bad sensor.

I hope you have a free retest coming. If not, try the station on Grandview and Washington Blvd.. They seem to have the best price in the area. I assume you have a "Test Only" directed vehicle. I work at a "Test and Repair" in MDR.

 

When I was emission testing in Missouri, if the Series XJ and XJ 40 had too light of oil ( 10/30W instead of 20/50W ) it would throw the Bar 90 into fail. When oil was changed and warmed, they passed test. This is after all cars were tuned and driven to warm.

 

Hi zenidyle,jchavez76 and jagfixer, OK, why 3 cats ? The first 2 turned out to be the cheap, one time fix, type. Although I didn't know, at the time. This one is pukka. I can see that a rich condition is indicated but, the plugs do not show this. The NOx figures, measure varying from 2 to 134, does not make sense to me.CO figure was up on the '10 readings but within allowable limits. I have just had an oil change and it has 10/40 (did this before jagfixers reply). The next test is the retest, I will post results. The heated O2 sensr goes in this week, Although now, the only codeshowing is '99'.
You've had some nice cars in your stable there jagfixer. My personal favourites were the MK2, 3.4, XK 150 and EType 4.2 (1965). I had them all in England.........Roger.

 

Hi all, would removing the air filter help the test results ?......Roger.

 

What I have been said in my first post is belove:
"I don't know what you had been done trouble shooting on your car but anyways, I would recomment these things need to do first before doing further trouble shooting, otherwise your head will spin like nuts with your money.
1/ Tune up: spark plugs, Wire set, distrubutor cap, distrubutive rotor, check map air flow sensor ...." That mean you also have to check following : air filter, fuel filter, check and correct timing, check and clean all GND, check for good alternator, battery, engine oil, transmission fluid.

 

zenidyle, I had checked all the things you mentioned, with the exception of the engine oil, which has now been changed. The air filter looked good but, it's not new and, so I wondered if testing it without, might be an idea,as normally this tends to lean out the mixture.......Roger.

 

So, that's good that you had checked all steps of tune up procedure. Now, the words you said:
"so I wondered if testing it without, might be an idea,as normally this tends to lean out the mixture......." It's not good ideas if you want to test it without air filter because Your engine already produced high NOX. Now you want to test it without air filter that mean you help your engine run more lean. The lean fuel mixtures is one of the reasons cause high NOX. Lean fuel mixtures exists when more air than necessary is added in mixtures and less fuel than requirement of mixtures is deliveried into combustion chamber. So in either case, lack of gasoline needed to make the cool combustion chamber down is not present. The more air to help easy detonation and combustion chamber temperatures increases quickly over 2500°F causing high nitrous oxide emissions (easy to produce NOX). Therefore, Automotive in engineering designer made in the EGR valve to reduce NOX.
So, now we are going to control your engine run lean out fuel mixtures. First of all, I am thinking about vacuum leak. You have to be patien and look carefully check all vacuum lines for cracking, loosing connection.... if all look good, I am suspecious the intake manifold gasket leak. This defect gasket is allowed the air by pass the air flow meter or MAP sensor. ECU has feed back wrong data from those sensor and think that the engine is less breath. By the time, ECU delivery signal to the fuel injectors to inject less fuel into combustion chamber. Finally, your engine run lean. More air draw into combustion chamber, least fuel to make cool combustion chamber, engine temperatures quickly rise up over 2500°F, result the high NOX produce.
Of cause, The air flow meter, MAP, Coolant temperature sensor, EGR valve, O2, fuel filter, fuel regulator could be one of the culprits to cause your engine run lean. However, we don't want you replace all those components above. So you need a visual inspection, clean it, Ohms out according to specs one by one to rule out which one is malfunction and replace its.
The last thought is High Engine Mileage with built up carbon. You did not say how many mile in your so I assume that your engine is high mileage. Over an engine's lifetime, carbon build-up develops in the engine's combustion chambers. The more miles on your engine, the more carbon build-up on the pistons, cylinder heads and valves. Carbon build-up decreases the available space for the air/fuel mixture to combust, and causes higher cylinder compression. High compression results in high temperatures and high NOx. So you have to decarbonizing the combustion chamber to increase combustion space, lower compression and reduce NOX. In order to do decarbonizing, there are many ways to do this but I would recomment use seaform to pour into vacuum line and maintain engine at 2000RPM for a while. Good lucks

 

Now I'm toally confused. First, you said it was running rich, now you say lean. Tha car has done 74000 miles and, the head gasket was replaced less than 5000 miles ago, with the attendant decoking etc. The Jaguar specialist said the engine was in perfect condition and needed no further work. I replaced the MAP sensor a couple of years ago, it was easy to recognise the faulty one, by watching the instant fuel consumption figures.EGR is clean,fuel filter is new, the O2 sensor will be fitted this weekend, I put a bottle of C&C through it prior to the test. HC readings have always been high on this car, even when there was 35000, on the clock, but NOX have always been low or zero,until this time when it registered 2 at 25 mph and 134 at 15 mph ! (I'm very suspicious of that high figure). Refering to the Lambda figures , why did you change your mind from rich (to which jchavez agreed) to lean ?........Roger.

 

OK, first, I thought that you make me confuse to change my mind because I keep following your post said:"...as normally this tends to lean out the mixture......." We are miscommunication together. I thought that you are fixing the car and everytime after fixing, you retest and got fail different result. However, you gave us some extra information in your car that would help us easy to discuss.
I even thought that you already replaced O2 but actually not done yet. So anyways, I would like to see new test result after you put new O2 on and retest it. Sorry make you confuse but I try to help you out. Please let us know the new result.